Theoretical And Experimental Research On The Control Of Femtosecond Laser Focal Field Aspect Ratio

ABSTRACT:Compared with traditional processing techniques, femtosecond laser microprocessing technique has such unparalled advantages as a high intensity, less heating effect and a lower damage threshold that can actually realize the three-dimensional processing of the microstructure. Femtosecond laser microprocessing technique has been widely applied to micro-nano processing in various fields. As requirements vary in the actual work of processing, femtosecond laser can not cater to various requirements because its single distribution of focal and energy fields restrain its processing ability and efficiency. This article is mainly about the methods of focal field aspect field control in femtosecond laser processing. It calculates the main parameters in various control methods of focal field from a theoretical basis. Through experiments, the feasibility and applicability of these parameters has been verified and using slit or diaphragm to processing of the deep hole in metals and of the waveguide cyclo-section has been carried out with the focal field control methods, the main contents are listed as follows:1. The method of applying "aspect ratio" to measure the cross section is proposed through analyzing the energy distribution of the focal field of the femtosecond laser focus. This article also makes an analysis on the relationship between the focal field energy distribution and the aspect ratio in processing.2. The influence that the main parameters of four different focus control methods have on the results of processing are analyzed and the figure relationship model between the focus control methods and the corresponding processing results with the later verification of the theoretical calculation is built through experiments.3. The research of deep hole processing in metals is carried out to analyze the restraint factors in the processing. After that, the article proposes a method which inserts the diaphragm to change the distribution of focal field energy. This method, together with the proper choosing of the diaphragm aperture, has succeeded in processing metal microporous with aspect ratio is20.4. The research into cyclo-section waveguide processing is carried out to analyze the influence that vertical and transversal direct-writing methods have on the shape of the waveguide-processed cyclo-section. The theoretical calculation of the relationship between the width of the slit inserted and the waveguided section is made. The performance of the optical waveguide processed by the slit method is tested and analyzed.